LED/LCD DOESN'T TURN ON

What voltage do you get from the battery both when it is on and off (battery must be fully charged for this)?

I get different voltage outputs when switching the battery on and off

I have a 36V battery but I get 28V-32V when the battery is both on and off

I have a 48V battery but I get 38V-44V when the battery is both on and off

I get 0V when the battery is both on and off